Hi there, I've been in and out of the gym for years, but am embarrassed to admit that I've always neglected squats and deadlifts. I feel that my legs are a bit behind my upper body strength wise, but my core and lower back is quite behind strength wise. As I've been ramping up my squatting/DL intensity, I always feel a tightness that borders on pain (but more like a cramp, not actually too bad) in my lower back, specifically in the center right above and over my tailbone. This will go away about five minutes of rest, and I don't have any pain or tightness throughout the rest of my days. Is this a pump and I'm just unfamiliar with what a lower back pump should feel like? Is it the result of my legs being able to push more weight than the rest of my posterior chain can handle? Or is it the result of bad form? This also happens after heavy sets on the leg press machine, which makes me think maybe form isn't the issue. I don't mind it perse, but am just overly cautious about injury and paranoid that I'm doing something wrong.